A hot-melt adhesive has been increasingly used in various fields because of excellent high-speed coating property, rapid curing property, solventless property, barrier property, energy saving property, economic performance and the like. A generally usable hot-melt adhesive is exemplified by a composition containing: a base polymer such as a styrene-isoprene-styrene block copolymer and a hydride thereof; a tackifier resin; and a plasticizer. As the tackifier resin, a hydrogenated petroleum resin and the like are used. The hydrogenated petroleum resin used for the tackifier resin requires tackiness. For instance, there has been proposed a manufacturing method of a hydrogenated petroleum resin starting from a cyclopentadiene compound and a vinyl aromatic compound (start materials), where a residual amount of a low-molecular-weight component in the hydrogenated petroleum resin (product) is controlled (for instance, Patent Literature 1).
In such a hydrogenated petroleum resin, volatile components such as unreacted monomers, a solvent, and low-molecular-weight components remain in a reaction mixture. Since the volatile components deteriorate a quality of the product, the volatile components need to be removed so much as not to adversely affect a quality of the product. Accordingly, a method of removing the volatile components from the reaction mixture using a so-called thin-film evaporator is generally employed.